Femtosecond Laser Inducing Micro/Nano Structures On The Metal Surface And Its Optical Properties

Recently, femtosecond laser direct inducing micro/nanostructures on metal surface has been demonstrated to be a promising technique for producing surface micro/nanostructure, the surface structures dramatically modify the optical properties of metal surface. The metals with micro/nanostructures on surface created in this work have tremendous potential in various technological applications, such as solar-driven thermoelectric generators, solar energy absorbers, thermal radiation sources, detectors and bio-optical devices.This paper mainly presented the experimental study on inducing mircro/nanostructure on metal surface by employing methods of fixed irradiation and scanning irradiation. It was found that nanostructure-covered laser induced periodic surface structures (NC-LIPSSs) was produced on metal Al surface through accumulation pulses under the experiment of fixed irradiation. The calculated result of numerical study by the Maxwell-Garnett theory of effective media and the two-temperature model effectively explained our experimental observations. Meanwhile, the experiment of scanning irradiation inducing large area micro/nano structure on metal surface was also presented. Seven different color were created on aluminum alloy surface by changing experiment conditions, included black, grey, brown, old wood, white, light golden and dark golden. Large area nanoscale grating structures was also produced on molybdenum surface, that made it exhibit different colors at different viewing angles. In addition,"black metal" were successfully produced on the metal surface of aluminum alloy and titanium, the reflectance measurement of them showed their reflectance can be controlled less than10%in the UV, vis, and IR wavelength ranges(200-2500nm). The last part of this paper discussed the physical mechanism of surface mico/nanostrutures influence on the color and absorption of the metals.